On Monday, December 25, 2017 at 1:20:57 PM UTC-7, Phillip Helbig (undress to reply) wrote:
In article , Gary
Harnagel writes:
The "arguments" from the "other side" are taken as FACT:
https://www.space.com/52-the-expandi...-to-today.html
space.com is hardly the best place to see what scientists really
believe.
"The universe was born with the Big Bang as an unimaginably hot, dense
point. When the universe was just 10-34 of a second or so old -- that
is, a hundredth of a billionth of a trillionth of a trillionth of a
second in age -- it experienced an incredible burst of expansion known
as inflation, in which space itself expanded faster than the speed of
light."
Yes, this is the standard idea.
Which came from space.com, so I don't understand your snide comment.
The only argument I see FOR inflation is the uniformity of the CMBR.
The fact that the CMB power spectrum looks like what one would predict
from amplified quantum fluctuations is another good argument. ANY good
theory has to explain the uniformity of the CMB.
Steinhardt's idea is one BIG quantum fluctuation.
Steinhardt has another take on it.
That's fine. The way forward is to propose experiments which will
distinguish between hypotheses.
It's hard to propose experiments for something SO big. What Steinhardt
needs are some little predictions, though.
As for Lemaitre, he had a hypothesis
which went beyond what was known at the time; it was not a rival to
another hypothesis attempting to explain the same thing.
So he was a smart guy and found a way to propose a theory consistent with
both GR and his religion.
Yes, Lema=EEtre was a priest, but the idea that he favoured the big bang
since it is consistent with his theology goes against all we know about
him.
You think his belief system had NOTHING to do with it? Each of us has our
own model of the universe that we have developed over our lives. I have
mine and you have yours ... and Lemaitre had his.
Sure, but not so dense that collapse is inevitable. And it doesn't
matter that quantum effects "may" prevent a singularity. It's unlikely
that they can be responsible for an expansion.
Who said that they are?
I think we'll have to look outside our universe for the that, but it COULD
be quantum effects (brane theory is a quantum theory).
It seems to me that expansion is possible only if the initial size/mass
is great enough (i.e., greater than the Schwarzschild radius.
The Schwarzschild radius is not applicable here; it is applicable in
static asymptotically flat space-times.
It seems to be quite close to that now. Why propose that it was different
in a past that we can't detect?
Note that a mass with density only that of water and with a radius out
to the asteroid belt would form a black hole from which nothing could
escape.
There are various estimates for the mass of the universe:
http://hypertextbook.com/facts/2006/...cPherson.shtml
varying from 1e50 to 1e60 kg (I'm ignoring the entry that proposes
infinity).
For the mass range indicated, the Schw. radius varies from 16000 to 160
trillion light-years, it being 1.6 billion light-years for M = 1e55 kg.
Don't be confused by dimensional analysis;
That's NOT "dimensional analysis." You might repeat your claim that the
Schwarzschild model doesn't apply.
the universe is not a black hole, even if it is dense enough.
How do you know this?
So what do you think obviates infinite density?
The answer will be given by a theory of quantum gravity. Do you have
one?
Not me! :-)
There is no new physics at the poles. You just need a different math.
In the case of cosmology, are you hoping for a new mathematics or a new
physics? Steinhardt's theory proposes a new physics, but he needs a new
mathematics to make predictions to validate his theory.
He needs falsifiable predictions to which can differentiate his theory
from others.
Indeed. There are quantum gravity theories that equate to GR in the weak
field. String theory is one of them. But perhaps they'll only get
differentiation under conditions we can never find without our own black
hole to play with.